For what it worth. I noticed a big difference in notification timing between Outlook and Droid. My Droid notify me at least 20 to 30 minutes ahead of Outlook (Outlook is set to receive every 3 minutes)
Did you notice something similar?
<edit> thanks to friendly sticky, changed deterrence to indeed difference, don't know where it came from!</edit>
[edited by: henry0 at 12:42 am (utc) on May 31, 2012]
Probably a difference in your web host having a temporary connectivity issue or your web server processing a ton of spam. If a spammer is hammering on a mail server gateway it can easily slow mail delivery down from seconds to hours.